Induction Heating Power Supply Research Articles

Research on a New Inverter Control Strategy of Induction Heating Power Supply

To achieve “high voltage, low current” in the induction heating power circuit, enhance the flexibility of component selection in the circuit, and improve the quality of the inverter’s output waveform, a new control strategy of a single-phase NPC three-level inverter with unipolar frequency-doubling SPWM method is proposed. With the series connection of IGBTs in a single-phase NPC three-level inverter, the voltage withstand requirement of IGBT is reduced by half. The middle four IGBTs are controlled using unipolar frequency-doubling SPWM, while the outer four IGBTs are turned on later and turned off earlier to address the neutral point voltage imbalance issue in the inverter. Simulation results show that, compared with the traditional bipolar SPWM-controlled single-phase full-bridge inverter, the DC-side input voltage of the inverter can be double, and the current flowing through the entire circuit can be halved under the same output power using the proposed method.

Improved study on double closed-loop control of three-phase PWM rectifier based on induction heating rectifier side

With the development of power electronics technology, induction heating power supply becomes more applicable. The three-phase PWM rectifier is widely used in induction heating system because of its advantages of better power factor and bi-directional energy transfer, and often adopts the control method of voltage outer loop and current inner loop to improve its control performance. However, the traditional rectifier control structure in the application process will appear such as poor anti-interference ability, low fault tolerance and other outstanding problems. In this paper, an improved H∞ controller is designed for the induction heating system based on the rectifier-side power regulation by combining the robust control principle, establishing a state space model of the system with an equivalent series resonant load, firstly decoupling the linearization of the model, and then designing a double-closed-loop PI controller as well as an improved current inner-loop H∞ controller based on the decoupled model. In order to facilitate the analysis, the PI controller and the H∞ controller are simulated under two kinds of starting conditions, and the comparison further confirms that the improved system has better anti-interference ability and dynamic characteristics.

Validation of a Temperature-Feedback Controlled Automated Magnetic Hyperthermia Therapy Device.

We present in vivo validation of an automated magnetic hyperthermia therapy (MHT) device that uses real-time temperature input measured at the target to control tissue heating. MHT is a thermal therapy that uses heat generated by magnetic materials exposed to an alternating magnetic field. For temperature monitoring, we integrated a commercial fiber optic temperature probe containing four gallium arsenide (GaAs) temperature sensors. The controller device used temperature from the sensors as input to manage power to the magnetic field applicator. We developed a robust, multi-objective, proportional-integral-derivative (PID) algorithm to control the target thermal dose by modulating power delivered to the magnetic field applicator. The magnetic field applicator was a 20 cm diameter Maxwell-type induction coil powered by a 120 kW induction heating power supply operating at 160 kHz. Finite element (FE) simulations were performed to determine values of the PID gain factors prior to verification and validation trials. Ex vivo verification and validation were conducted in gel phantoms and sectioned bovine liver, respectively. In vivo validation of the controller was achieved in a canine research subject following infusion of magnetic nanoparticles (MNPs) into the brain. In all cases, performance matched controller design criteria, while also achieving a thermal dose measured as cumulative equivalent minutes at 43 °C (CEM43) 60 ± 5 min within 30 min.

Efficiency analysis and heating structure design of high power electromagnetic thermal energy storage system

Based on the principle of electromagnetic induction, this paper proposes a new sleeve structure of electromagnetic induction heating energy storage system, which converts the electrical energy that cannot be consumed by wind power, solar power and other power grids into heat energy. The electromagnetic induction heating model of the eddy current field is established by Ansoft/Maxwell, and the magnetic induction intensity, current penetration depth and current frequency are analyzed. The three-dimensional fluid temperature field and its corresponding temperature characteristics of the system are analyzed by Ansys/Fluent. The temperature field cloud diagram of the sleeve is analyzed. It is concluded that with the increase of air thickness, the loss of the internal iron pipe increases, and the loss of the middle iron pipe decreases. The characteristic curve of the resonant circuit of the electromagnetic induction heating power supply is simulated and analyzed to determine the optimal parameters of the resonant circuit of the induction heating. A 100 kW electromagnetic energy storage system is developed, and the effectiveness and practicability of the method are verified, which can be applied to high power thermal energy storage.

The invention relates to an intermediate frequency power supply fast start and digital phase locked loop control technology

Intermediate frequency induction heating is widely used because of its low energy consumption and high thermal efficiency, but the speed of traditional intermediate frequency power supply is slow and its frequency tracking accuracy is limited. In order to maintain the resonant state of the load during the working process of the induction heating power supply and realize the automatic frequency tracking control during the working process. The frequency tracking of the 40kW intermediate frequency power supply is researched, and a method of combining the resonant frequency automatic identification algorithm and the digital phase locked loop frequency tracking control method is proposed. MATLAB simulation and experiment show that the system based on this control method can save the time of searching the load resonance frequency in the initial stage of the power supply, improve the frequency tracking speed, accelerate the dynamic response speed of the system, avoid the failure of frequency lock, and play the role of fast and stable startup.

3상 3스위치 PWM 전류원 정류기를 이용한 고역률 단조용 유도가열 전원 장치

Induction heating can convert electrical energy to thermal energy with high conversion efficiency and quick heating. Currently, a current source rectifier/inverter-fed parallel resonant circuit is widely used as an induction heating power supply for forging applications. Conventional induction heating power supplies have low power factor characteristics and high input power current THD characteristics, or have disadvantages of complicated control and high price. In this paper, we propose an induction heating power supply using a three-phase three-switch PWM rectifier to compensate for the above-mentioned shortcomings. The power factor of the input stage is kept close to 1, and the DC link current is uniformly well controlled regardless of fluctuations in the load voltage. In addition, through the SOGI PLL & FLL control algorithm, the current source inverter tracks the frequency and phase of the load resonance voltage well. The prototype of the induction heating power supply is designed and manufactured with a rated power of 40 kW and its characteristics and performances are confirmed through the experimental results. The proposed induction heating power supply using the three-phase three-switch PWM rectifier is expected to be widely used in the forging applications.

Analysis of Phase Transformation and Mechanical Properties of 55CrMo Steel during Induction Hardening

Abstract To optimize the parameters of induction hardening and improve the surface hardness distribution of ball screw, the effects of the induction heating temperature on the microstructure and mechanical properties of 55CrMo steel were investigated. The specimens were heated up to 800°C, 850°C, 900°C, 950°C, 1,000°C, or 1,100°C by the induction heating power supply. Microstructural characterization of specimens was performed using an optical microscope and a high-resolution scanning electron microscope. The volume fraction of the retained austenite was measured using an X-ray diffractometer. The mechanical properties were evaluated by a microhardness tester and an electronic universal testing machine. The results show that the volume fraction of martensite in the hardened specimen increases with the increasing of heating temperature. A mixed microstructure consisting of ferrite + pearlite, bainite, and martensite is produced because of the nonfully and nonuniform austenitic state of original microstructure as the heating temperature is at 800°C. A full martensite can be produced as the heating temperature is more than 850°C. The volume fraction of retained austenite in the hardened specimen is lower when the heating temperature is in the range of 850°C–950°C; nonetheless, the volume fraction of retained austenite increases, and the tensile strength of the specimen reduces with the increasing of the heating temperature when the heating temperature is more than 950°C. The 55CrMo steel has good microstructure and mechanical properties and can meet the requirements of ball screw when the induction heating temperature is in the range of 850°C–950°C.

Intelligent Control Method of Power Supply for Tundish Electromagnetic Induction Heating System

An intelligent control method is proposed to improve the performance of power supply for tundish electromagnetic induction heating, which can adequately regulate the tundish temperature. The topology structure of power supply for tundish electromagnetic induction heating is presented, and its working principle is analyzed. The power supply consists of six power units, and each of them consists of a fore-stage three-phase rectifier and back-stage single-phase inverter. The feedforward control DC voltage is used by three-phase rectifier to obtain the stable DC voltage supplied to the inverter. The cloud controller based intelligent temperature control algorithm is combined with the power feed-forward algorithm to obtain accurate tracking of the output current and constant temperature control of the tundish steel in the back-stage inverter. The simulation and experiment are performed to verify the accuracy and effectiveness of the proposed method.

A Compact and Cost Efficient Multiconverter for Multipurpose Applications

This paper presents a novel single-phase to single-phase multiconverter topology that can be applied in multiple areas. The proposed multiconverter is designed with only two soft power semiconductor switches (e.g. MOSFET or IGBT), four power diodes and a center-tapped transformer which makes it more compact in size, decrease the gate driving complexity, reduce the total equipment costs and enhance the energy conversion efficiency with minimized losses. Furthermore, the utilization of the transformer in the proposed converter mitigates the multiple AC source requirement problems and provides galvanic isolation which increases the reliability of the converter. Moreover, the presented multiconverter is applicable in various areas including electric traction as a speed controller, induction heating, AC and DC variable power supplies, etc. which signify the competence of this converter in energy conversion appliances. However, a comparative analysis of the offered converter with the existing AC-AC converters is also introduced in this paper with respect to the number of components, equipment costs, gate driving complexity, and application areas. In order to evaluate the performance of the proposed multiconverter, the simulation-based results carried out in MATLAB/Simulink are presented and analyzed in this paper with proper descriptions. Finally, a scaled-down prototype is developed in the laboratory to validate the simulation results and the feasibility of the proposed multiconverter.

Design and construction of a Maxwell-type induction coil for magnetic nanoparticle hyperthermia

Purpose We describe a modified Helmholtz induction coil, or Maxwell coil, that generates alternating magnetic fields (AMF) having field uniformity (≤10%) within a = 3000 cm3 volume of interest for magnetic hyperthermia research. Materials and methods Two-dimensional finite element analysis (2D-FEA) was used for electromagnetic design of the induction coil set and to develop specifications for the required matching network. The matching network and induction coil set were fabricated using best available practices and connected to a 120 kW industrial induction heating power supply. System performance was evaluated by magnetic field mapping with a magnetic field probe, and tests were performed using gel phantoms. Results Tests verified that the system generated a target peak AMF amplitude along the coil axis of ∼35 kA/m (peak) at a frequency of 150 ± 10 kHz while maintaining field uniformity to >90% of peak for a volume of ∼3000 cm3. Conclusions The induction coil apparatus comprising three independent loops, i.e., Maxwell-type improves upon the performance of simple solenoid and Helmholtz coils by providing homogeneous flux density fields within a large volume while minimizing demands on power and stray fields. Experiments with gel phantoms and analytical calculations show that future translational research efforts should be devoted to developing strategies to reduce the impact of nonspecific tissue heating from eddy currents; and, that an inductor producing a homogeneous field has significant clinical potential for deep-tissue magnetic fluid hyperthermia.

전류원 PWM 정류기 / 인버터를 이용한 새로운 단조용 유도가열 전원장치의 제어회로 설계

The conventional thyristor current source rectifier/inverter-fed parallel resonant circuit widely used for induction heating of forging applications has low power factor and high THD at the input side. Because of these disadvantage the IGBT PWM current source rectifier and inverter has been recently studied as an induction heating power supply topology. Therefore, this paper proposes the design method of power factor controller, the new detecting method of current and voltage for use in system control, and also the technique to follow the resonance voltage of the tank circuit for inverter switching. The proposed techniques are implemented in a 40㎸A induction heating power supply and its performances are verified through experiments. It is expected to be used extensively in induction heating power supply systems for forging with wide power range.

The Analysis of Numerical Simulation About Thermal Management on Frequency Converter

For the heat loss of frequency converter in 50KW class medium-frequency electron magnetic induction steam generator system, this study explored a new solution for inverter cooling and waste heat recovery, which solved the problem of coolant temperature rise while replacing the cooling water, meanwhile recovered part of the waste heat for re-production. The heat dissipation of the power device is simulated to analyze the rationality of the heat dissipation system structure, and the thermal resistance equivalent circuit is established to realize the accurate calculation of the temperature at each point in the system. Experimental research under different environmental temperatures, power, and total cooling water conditions has been done to test and verify its function, the findings show that the designed heat dissipation system for the medium frequency induction heating power supply device works well, which makes the temperature of all pivotal devices converge to normal operating temperature range and increases the energy efficiency of the system by about 4%. The proposed cooling scheme is suitable for promotion in heating projects with high power equipment.

Development of Series Resonant Inverters for Induction Heating Applications

This paper proposes a cost-effective series resonant inverter employed in applications of induction heating. The proposed inverter operates with high-frequency pulse-density modulation strategy for soft-switching. The high-frequency operation (20 kHz – 100 kHz) of this inverter results in a nearly sinusoidal output that is suitable for relatively fixed output applications such as induction heating. The series resonance circuit comprises an inductor and a capacitor that are in series with the load. The small size of resonating components is due to the high-frequency switching operation. The practical effectiveness of induction heating power supply is substantially proved by implementing a prototype series resonant inverter. To analyze the performance, comparison between the simulation and experimental results is done by using PSIM program

Development of Series Resonant Inverters for Induction Heating Applications

This paper proposes a cost-effective series resonant inverter employed in applications of induction heating. The proposed inverter operates with high-frequency pulse-density modulation strategy for soft-switching. The high-frequency operation (20 kHz – 100 kHz) of this inverter results in a nearly sinusoidal output that is suitable for relatively fixed output applications such as induction heating. The series resonance circuit comprises an inductor and a capacitor that are in series with the load. The small size of resonating components is due to the high-frequency switching operation. The practical effectiveness of induction heating power supply is substantially proved by implementing a prototype series resonant inverter. To analyze the performance, comparison between the simulation and experimental results is done by using PSIM program

Constant temperature control of tundish induction heating power supply for metallurgical manufacturing

The tundish induction heating power supply (TIHPS) is one of the most important equipment in the continuous casting process for metallurgical manufacturing. Specially, the constant temperature control is greatly significant for metallurgical manufacturing. In terms of the relationship between TIH load temperature and output power of TIHPS, the constant temperature control can be realized by power control. In this paper, a TIHPS structure with three-phase PWM rectifiers and full-bridge cascaded inverter is proposed. Besides, an input harmonic current blocking strategy and a load voltage feedforward control are also proposed to realize constant temperature control. To meet the requirement of the system, controller parameters are designed properly. Experiments are conducted to validate the feasibility and effectiveness of the proposed TIHPS topology and the control methods.

Analysis and control of tundish induction heating power supply using modular multilevel converter

Modular multilevel converters (MMCs) provide advantages to reach medium-voltage operation increasing the power level in industrial applications. In this study, a tundish induction heating power supply based MMC (MMC-TIHPS) is investigated for heating molten steel. The equivalent model of MMC-TIHPS is established and the energy in horizontal and vertical directions are analysed. The heating control for molten steel consists of temperature increasing and constant temperature processes (alternatively called transient-state and steady-state operation). The main contribution of this study is to propose a direct power feedforward control based load current feedforward strategy for TIHPS. With this strategy, TIHPS can be controlled operating with full power to heat molten steel in transient state and guarantee the insulation effectiveness in steady state. Proper parameters of controllers are designed. Experimental results are conducted to validate the feasibility of MMC-TIHPS and the effectiveness of the proposed control method.

System design and engineering for baking of the KTM vacuum vessel

In tokamaks, residual gases and especially water vapors adsorbed in shell pores are removed by baking the vacuum vessel (VV) and in-vessel elements to a temperature not lower than 200 °С. The combined method for VV baking is proposed for the KTM tokamak, namely, baking by ohmic heaters to heat the outer shell of the vacuum vessel (the main method) and by eddy currents induced, mainly, in the inner shell by the central solenoid (CS) (additional induction method). To realize the proposed method the authors have developed the baking system consisting of active heaters arranged on the VV outer shell and an AC source supplying the central solenoid initiating eddy currents in the shell of the VV inner cylinder. The process of the KTM VV baking was numerically simulated by the numerical simulator developed by the authors. As a result, (a) the baking scenario has been defined, which satisfies the requirements both for the process duration and for the temperature non-uniformity; (b) the requirements have been formulated for the induction heating source and power supply source of the outer heaters.

Design of New Induction Heating Power Supply for Forging Applications Using Current-Source PWM Converter and Inverter

Design of New Induction Heating Power Supply for Forging Applications Using Current-Source PWM Converter and Inverter

Improved Litz wire manufacture process using resonant power converter-based induction heating

PurposeLitz wire manufacturing using mechanical procedures presents several limitations regarding reliability and repeatability, especially when a small strand diameter is used. This paper aims to propose a power supply design for Litz wire manufacturing using a high-frequency high-performance resonant converter.Design/methodology/approachThis paper proposes the design of a resonant power supply for induction heating specially designed to tackle with the challenge of heating Litz wires quickly.FindingsThe proposed converter enables the removal of the isolating coating from the Litz wire through induction heating, improving significantly the manufacturing process.Originality/valueThe proposed converter improves significantly the manufacturing process of Litz wire through induction heating, with economic and reliability benefits.

Design of power converters for induction heating applications taking advantage of wide-bandgap semiconductors

PurposeWide-bandgap (WBG) semiconductors have emerged as a disruptive technology in the power electronics sphere. This paper aims to analyse and discuss the importance for induction heating systems and gives some examples and highlights some future design trends and perspectives.Design/methodology/approachThe benefits of WBG semiconductors are reviewed with a special emphasis on induction heating applications.FindingsWBG devices enable the design of higher-performance induction heating power supplies. A significant selection of the reported converters is discussed, highlighting the benefits of this technology.Originality/valueThis paper highlights the benefits of WBG semiconductors and their potential to change and improve induction heating technology in the next years.